Journal Article

Peroxisome biogenesis initiated by protein phase separation

Michnick, Stephen W., Bacellar, Isabel O. L., Zhang, Zhenghao, Wahba, Haytham M., Castellanos-Girouard, Xavier, Kisley, Lydia, Omichinski, James G., Ravindran, Rini

2023

Overview

Peroxisomes are organelles that carry out β-oxidation of fatty acids and amino acids. Both rare and prevalent diseases are caused by their dysfunction 1 . Among disease-causing variant genes are those required for protein transport into peroxisomes. The peroxisomal protein import machinery, which also shares similarities with chloroplasts 2 , is unique in transporting folded and large, up to 10 nm in diameter, protein complexes into peroxisomes 3 . Current models postulate a large pore formed by transmembrane proteins 4 ; however, so far, no pore structure has been observed. In the budding yeast Saccharomyces cerevisiae , the minimum transport machinery includes the membrane proteins Pex13 and Pex14 and the cargo-protein-binding transport receptor, Pex5. Here we show that Pex13 undergoes liquid–liquid phase separation (LLPS) with Pex5–cargo. Intrinsically disordered regions in Pex13 and Pex5 resemble those found in nuclear pore complex proteins. Peroxisomal protein import depends on both the number and pattern of aromatic residues in these intrinsically disordered regions, consistent with their roles as ‘stickers’ in associative polymer models of LLPS 5 , 6 . Finally, imaging fluorescence cross-correlation spectroscopy shows that cargo import correlates with transient focusing of GFP–Pex13 and GFP–Pex14 on the peroxisome membrane. Pex13 and Pex14 form foci in distinct time frames, suggesting that they may form channels at different saturating concentrations of Pex5–cargo. Our findings lead us to suggest a model in which LLPS of Pex5–cargo with Pex13 and Pex14 results in transient protein transport channels 7 . A study presents evidence to support a model in which liquid–liquid phase separation of components of the transport machinery mediates formation of transient protein transport channels on peroxisomes.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 14 / 14/19 / 14/34 / 14/35 / 631/57/2268 / 631/57/2269 / 631/80/2023/2022 / 631/80/642/2013 / 82 / 82/1 / 82/29 / 82/83 / Amino acids / Cargo / Cross correlation / Fatty acids / Foci / Humanities and Social Sciences / Hypotheses / Imports / Intracellular Membranes - chemistry / Intracellular Membranes - metabolism / Intrinsically Disordered Proteins - chemistry / Intrinsically Disordered Proteins - metabolism / Liquid phases / Membrane proteins / Membrane Proteins - chemistry / Membrane Proteins - metabolism / Membranes / multidisciplinary / Nuclear pores / Organelles / Oxidation / Peroxins - chemistry / Peroxins - metabolism / Peroxisome-Targeting Signal 1 Receptor - chemistry / Peroxisome-Targeting Signal 1 Receptor - metabolism / Peroxisomes / Peroxisomes - chemistry / Peroxisomes - metabolism / Phase separation / Phase Transition / Polymers / Protein Binding / Protein Transport / Proteins / Saccharomyces cerevisiae - chemistry / Saccharomyces cerevisiae - cytology / Saccharomyces cerevisiae - metabolism / Saccharomyces cerevisiae Proteins - chemistry / Saccharomyces cerevisiae Proteins - metabolism / Science / Science (multidisciplinary) / Spectroscopy / Yeast